[Effect of toxins from the scorpion Buthus eupeus on the sodium channels of the membranes of nodes of Ranvier].

Effect of three toxins M3, M7 and M8 from Buthus eupeus poison on sodium channels of Ranvier node membrane of the frog was studied under potential fixation. Toxin M3 was found to produce no effect on sodium currents of Ranvier node membrane of the frog. Inactivation kinetics difference between normal and modified sodium channels was used in estimating a fraction of toxin-modified channels. The toxins were found to interact with the channels in the ratio 1 : 1, the dissociation constants for M7 and M8 equalling 1.7 . 10(-7) M and 0.9 . 10(-9) M respectively. Dependence of the effect of scorpion toxins on the membrane potential is stated.